Spray-drying is the standard method for manufacturing laundry detergent base powder. Typically, detergent ingredients are mixed together to form an aqueous detergent slurry in a mixer, such as a crutcher mixer. This slurry is then transferred through at least one pump to a spray nozzle, and the slurry is sprayed into a spray-drying tower, and spray-dried to form a spray-dried powder.
Typically, multiple chemically different formulations are manufactured on the same spray-drying equipment. This leads to the production of excessive quantities of unwanted material during the change over from one formulation to another. This is due to the need to flush the first formulation ingredients out of the spray-drying equipment, such as flushing the drop tank and pipe leading to the spray nozzle. In addition, there is an unwanted excessive time delay between manufacturing runs whilst this flushing is carried out. This reduces the overall efficiency and production capacity of the spray-dying process.
The Inventors have overcome the above problems by introducing a detergent ingredient, such as detergent ingredients that vary from one formulation to another, later in the spray-drying process, such as dosing them into the pipe after the drop tank. In addition, the inventors have found that by carefully selecting the dimensions, so as to carefully control, the volume of the pipe connecting the drop tank to the spray nozzle in relation to the volume of the drop tank, and in addition by carefully controlling the point at which the detergent ingredient is dosed into the pipe, the amount of flushing is reduced. This in turn means that the change over time between the production of different formulations on the spray-dying equipment is significantly reduced, and the overall efficiency and production capacity of the spray-dying process is dramatically improved.